Telephone system



April 10, 1934. R. TAYLOR TELEPHONE SYSTEM Filed Jan. 13, 1932 2 eets-Sheet l April 10, 1934. R TAYLOR 1,954,106

7 TELEPHONE SYSTEM Filed- Jan. 15, 1932 2 Sheets-Sheet 2 Patented Apr. 10, 1934 UNITED STATES PATENT OFFICE TELEPHONE SYSTEM Application January 13, 1932, Serial No. 586,402 In Great. Britain January 19, 1931 14 Claims.

The present invention relates to telephone systems and is more particularly concerned with systems in which a group of switches is controlled by common control equipment.

The value of such arrangements depends upon the fact that the period during which the switch is held for a conversation is much greater than the period required for operating the switch, any decrease in the holding time of the common equipment decreases the amount required and the object of the present invention is to provide an improved switch for use in systems of the above type which will not unnecessarily hold the control equipment and which moreover contains several improved features.

According to one feature of the invention in a telephone system employing common control equipment, when a final selector switch encounters a busy or like condition, it is immediately dissociated from the control equipment which is then restored to the service of other associated switches.

According to a further feature of the invention the test relay is arranged for operation by current flowing in one direction only so as to obviate the possibility of false connections when booster metering potential is encountered by the wipers of the switch during the setting operation.

According to another feature of the invention all busy connections will result in the rotation of the shaft and wipers of the switch to an extreme position where cam springs are operated to connect up the busy signal and eifect the operation of busy call trafiic recording meter.

The invention will be better understood from the following description of one method of carrying it into effect, reference being had to the accompanying drawings comprisin Figs. 1 and 2, of which Fig. 1 shows a final selector and Fig. 2 shows control apparatus associated with a group of final selectors such as the one shown in Fig. 1. It will be understood, however, that this particular embodiment is given by way of example only and that various modifications could be made by those skilled in the art without departing from the spirit of the invention.

Referring now to the drawings, it will be seen that the final selector shown may be taken into use over one of two sets of conductors shown extending from the left-hand side of Fig. 1. The particular set taken into use depends upon the destination of the call. When the switch is taken into use over the upper set of .conductors the upper set of wipers shown on the right-hand side of the drawings will be connested up so as to establish connection in the first hundred group. When the switch is taken into use over the lower set of conductors relay WS will be operated prior to the setting operation of the switch to connect up the lower set Oil of wipers so that connection may then be established in the second hundred group.

Assuming now that the switch is taken into use over the lower set of conductors then the following circuit will be completed for the operation of relay WS in series with relay AC in the control equipment: earth by way of the lower winding of relay WS, resting armature b8, conductor 10, calling circuit including the subscribers instrument, conductor 11, restingarmature b1, conductor 12, winding of relay AC in the control equipment, resting armature h? to battery. Relays WS and AC are therefore operated in the foregoing circuit, the former at light armature wsl completing a locking circuit for itself by way of the resting springs 21112 and the busy test jack springs BTJ to earth over the release trunk conductor 13 extending to the preceding switch. Moreover at armature ws2 an operating circuit is completed for relay K over its 10W.er winding, while at armatures ws3 ws4 and ws5 the lower set of wipers are connected up so that connection maybe established in the second hun dreds group. Relay K in operating at its light armature k1 prepares a locking circuit for itself which will become effective subsequently, at armatures 103 to It?! the control equipment is associated with the final selector circuit taken into use.

Returning now to the operation of relay AC at its armature (7401 an operating circuit is completed to relay BC which thereupon locks by way of its armature b0 1, and at armature 1902 extends earth from the resting springs of armature dcl over conductor 14 to maintain relay K operated, while a branch circuit may also be traced from conductor 14 by Way of the resting armature 175 and the resting springs zml to hold the preceding switches and maintain the guarding circuit; at armature bc3, relay C is operated on its right-hand high resistance winding, at armature 1104 a point is prepared in the impulsing circuit to the driving magnets of the switch, at armature Z705 an operating circuit is prepared to relay J while at armature bcfi an operating circuit is prepared to relays H and E. Relay C in operatingover the circuit to its right;- hand winding, at armature c1 prepares a fur ther point in the virnpulsing circuit to the driving magnets, atarmature 62 opens a point in the circuit to relay H and at armature 03 opens a point in the operating circuit to relay E. No further circuit changes will now take place until the first series of impulses is received, whereupon relay AC will impulse in synchronism therewith since it is included in the calling circuit to the subscribers instrument; upon the first fall away of its armature acl, earth will be extended by way of the low resistance left-hand winding of relay C, Fig. 2, operated armatures bo t and c1, resting armature e1, conductor 21, operated armature k3, resting springs NR2, winding of the vertical magnet VM to battery. The vertical magnet energizes in the circuit to raise the shaft and wipers to the first level whereat the off-normal springs designated N are operated. Springs N1 short-circuit the lower winding of relay WS so as to provide a more effective impulsing circuit, springs N2 prepare a point in the circuit of the release magnet ZM while springs N3 prepare a circuit for the operation of relay E which will become eifective later, and at the same time the initial energizing circuit to relay C over conductor 18 is opened. Since, however, relay C is equipped with a copper slug and its left-hand winding is included in the impulsing circuit to the driving magnet it will be appreciated that this relay is therefore held operated continuously during the impulsing period. Relay BC is slow to release and remains operated continuously during the impulsing period. At the end of the impulsing period when the shaft and wipers are standing opposite the desired level relay AC will hold operated for an extended period so that the circuit is held open to relay C, and upon the release of this latter relay the following circuit is completed to relay E to effect the transfer of the impulsing circuit to the ro tary magnet: earth at the resting springs NR1, Fig. 1, operated springs N3, operated armature k6, conductor 15, resting armatures h3, m2 and c3, winding of relay E to battery. Relay E at armature e1 transfers the impulsing circuit to the rotary magnet RM, at armature 62 completes a circuit for the re-operation of relay C and its right-hand winding, at armature e3 prepares a locking circuit for itself and at armature e4 prepares an operating circuit to relay RN. Relay C in re-operating disconnects the winding of relay H from the testing wiper during the rotation of the switch, and at armature 03 completes the locking circuit for relay E by way of its own operated armature 63 to earth at the operated armature Z706.

Considering now the circuit operations upon the reception of the second series of impulses corresponding to the units digit: relay AC releases in synchronism with the impulses and upon the first impulse the following circuit is completed to the rotary magnet RM: earth at the resting springs controlled by armature acl, low resistance left-hand winding of relay C, operated armatures bc, c1 and 61, low resistance winding of relay RN, conductor 16, operated armature Ice, winding of the rotary magnet RM to battery. In this manner the rotary magnet is energized to advance the wipers into engagement with the first set of bank contacts in the level chosen, at the completion of the first rotary step the rotary magnet springs rm are operated without effect at this time, while the rotary off-normal springs designated NR are also operated to fulfil various functions which will now be described. At the operated springs NR1, Fig. 1, the initial energizing circuit to relay C extending over conductor 15 is opened, but as already explained this relay will continue to hold operated during the impulsing period by reason of its copper slug and the inclusion or" its low resistance winding in the circuit of the driving magnet. At springs NR2 an operating circuit is prepared for relay B. It should also be mentioned that relay RN is operated in series with the rotary magnet RM and at its armature m1 provides a temporary locking circuit for itself, at springs r112 opens the initial energizing circuit to relay C, at armature m3 opens a point in the operating circuit to relay B, at armature m4 opens a further point in a circuit to the right-hand winding of relay C, and at armature m5 completes an alternative guarding circuit to the release trunk conductor 13. At the cessation of the units series of impulses, relay AC will again be held operated and upon the release of relay C after its slow period has elapsed the following circuit is completed to the lower winding of relay H: earth at the operated armature I706, operated armature 63, lower winding of relay H, resting armature 02, metal rectifier MRC, conductor 17, operated armature ic'Z, operated armature 2085, to the lower test wiper.

Relay E releases shortly after its locking circuit is opened at armature 03.

If the line of the wanted subscriber tests free the lower test wiper will, under these conditions, encounter battery by way of the subscribers bridge cut-olf relay (not shown) and under these conditions relay H will be operated in series therewith. Relay H in operating at its light armature hl completes a locking circuit to its upper Winding, at armature 7L2 direct earth is connected to the lower test wiper so as to busy the selected circuit against other switches, at armatures F23 and he ringing current is con nected to the calling circuit so as to signal the wanted subscriber, at armature hi5 a locking circuit is prepared to the ringing trip relay F, at armature b6 the booster battery metering circuit is connected up in readiness for the called subscriber to reply and at armature h? a leak on the main ringing circuit is provided by way of the low capacity condenser QA to the calling circuit so as to inform the calling subscriber that the call is proceeding.

Considering now the immediate ringing circuit in detail, this may be traced as follows: ringing generator connected to the resting armature 9'2, resting armature f2, operated armature 71.3, conductor operated armature k6, resting arma ture b3, operated armature ws3, line wiper, wanted subscribers instrument circuit, line wiper, operated armature ws i, resting armature b4, operated armature k5, conductor 18, operated armature he, resting armature f3, ringing return resistance VB to battery. In this manner, therefore, an immediate ring will be given as soon as the wanted line is connected with so that when a call has been extended to a private branch exchange, there shall be no possibility of the operator at the private branch exchange plugging into a line which was marked as idle, but has been subsequently seized, during an initial silent peiod of the ringing cycle. It has also the advantage that the called party given the opportunity of answering the call at an earlier time so that the holding time of the common equipment will be reduced. When relay E releases at the end of its slow period, relay J is then operated over armatures e4, ml, f4, cZcS and bc5. At armature 9'1 a circuit is completed to relay RN which it should be mentioned is sufficiently slow in releasing to remain operated during the interval between the release of relay C and the operation of relay J. Relay J moreover at armature 72 disconnects the continuous ringing circuit and in its place connects up the usual intermittent ringing circuit which is completed by way of the upper winding of relay F.

In connection with the metal rectifier MRC which is included in the operating circuit of relay H it should be explained that in case the test wiper should be rotated into engagement with a contact which happens to be connected to booster battery during the metering period, then the current in the testing circuit of relay H would then tendto flow in the opposite direction, and since the rectifier is connected up in such sense as to oppose current flow in this direction, it will be appreciated that relay H will not be falsely operated during these conditions. Alternatively, relay H could be replaced by a polarized relay when the necessity for the metal rectifier would not then arise since the relay alone would be sufficient to distinguish between a metering connection and an idle condition.

When the wanted subscriber removes his receiver to answer the call the direct current circuit so produced will permit relay F to operate over its upper winding, and when the armature fl, which it will be seen is normally short-circuiting the lower winding, opens its contacts, then the relay will look from battery by way of resistance YA in series with the lower winding to earth over operated armatures k5 and bc6.

Relay F moreover at armatures f2 and f3 disconnects the ringing circuit and connects the windings of relay DC to the upper and lower speaking conductors of the called line, at armature M the holding circuit is opened to relay J and at armature f5 the initial energizing circuit to relay BC is opened but the relay remains held over its armature bcl.

Relay DC operated over the called loop and at armature dcl substitutes booster battery in place of guarding earth to the release trunk conductor 13 so as to effect the operation of the called subscribers meter in the well-known manner, whilst maintaining the preceding switches operated. At armature dc2 a locking circuit is prepared which is not eilective at this stage, at armature dc3 a circuit is prepared to relay B which is effective upon the release of relay RN, and at armature (204 a point is opened in a self interrupted drive circuit to the rotary magnet which is not effective at this stage.

Due to the operation of armature f4, relays J and RN release in turn and upon the release of relay RN an operating circuit is completed to relay B over its right-hand winding and armatures m3, dc3 and D05. Relay B at its armatures b1, b2 and b8 completes the calling side of the speaking circuit, and at armatures b3 and b4 completes the called side of the speaking circuit. At armature b5 booster battery is disconnected from the release trunk and replaced by the usual guarding earth, at armature b6 direct earth is connected to the lower test wiper since that extended from the control equipment will be shortly disconnected, at armature b7 a circuit is prepared to the called subscriber held supervisory lamp CSH and also to the busy holding winding of relay B. Under these conditions, therefore, relays A and D are operated over the calling and called circuits respectively, the former at its armature almaintains an alternative holding circuit to relay B and the latter at its armatures d1 and d2 reverses the direction of current flow in the calling circuit for metering or supervisory purposes, and at armature d3 opens the circuit of the called subscriber held lamp CSH. Upon the operation of relay B, relays AC and DC release, relay AC opens the circuit of relay BC which in turn releases and removes earth from the holding circuits of relays H and F, which in turn release and the control equipment is now free for further use. Moreover upon the release of relay K which follows the release of relay BC the various make armatures associated with this relay are restored so as to dissociate the final selector switch in question from the control equipment.

Considering now the condition when a subscriber calls a spare or unallotted number, then the circuit operations will be the same as those previously described so far as the operation of relays H and. J. Under these conditions the lower line wiper will meet a battery from the unallotted number equipment and relay F will be immediately operated. As the circuit to the upper line winding of relay DC is not completed this relay will not be operated so that under these conditions the meter circuit will be ineffective. Relay F in operating as previously described causes relay J and relay RN to release in turn whereupon the circuit is then completed to relay B which operates to connect up the transmission circuit as previously explained. Under these conditions relay A is operated over the calling circuit to maintain relay B and a distinctive tone is extended from the unallotted number equipment connected With so as to inform the calling subscriber that the wanted number is unobtainable. Relays AC, BC and F in the control equipment restore, while upon the release of relay K the final selector taken into use is dissociated from the common control equipment.

Considering now the condition when the wanted subscriber is already engaged in a previous connection, then under these conditions the test wiper will encounter earth instead of battery and therefore relay H will not be operated; upon the release of relay E, relay J will operate and in turn hold operated relay RN in the manner previously described. With relay J operated and relay H not operated the following energizing circuit may be traced to the rotary magnet RM: earth at the operated armature bc6, resting armature h5, operated armature i3, resting armature c104, low resistance winding of relay RN, conductor 16, operated armature k4, winding of the rotary magnet RM to battery. The rotary magnet operates and advances the wipers on to the next set of bank contacts, at the conclusion of the magnet stroke the springs rm will make contact to energize relay DC on one winding over the circuit: earth at the resting armature al, Fig. l, operated armature k8, operated springs rm, conductor 19, operated armature 7'4, left-hand winding of relay DC to battery. Since, however, the resting armature 104 is included in the circuit to the rotary magnet RM, it will be appreciated that interaction will take place be tween the relay DC and the rotary magnet so as to advance the wipers automatically into an extreme position where the cam springs designated S are operated. Upon the next operation of relay DC after the springs 5 have been operated, a locking circuit may be traced as follows: by way of its operated armature (102 over conductor 20, operated springs S1, operated armaiii) ture k8 to earth at the resting armature a1. Under these conditions, therefore, the holding circuit to relay J, which is arranged to hold operated during the automatic stepping period is now definitely opened at armature ($03, so that the relay releases after its slow period and opens the circuit of relay RN to cause relay B to operate in a manner already described in connection with the circuit operations for the testing of a free line. Relay B in operating guards the switch and opens the cicuits of relays AC and DC to restore the control equipment, while upon the subsequent release of relay K the control equipment is dissociated from the final selector switch. The busy call traiiic recording meter OVF is operated over the test wiper and armatures b6 and 1085. At the operated cam springs S2 a holding circuit is prepared to the left-hand winding of relay B and at cam springs S3 a signalling circuit indicative of the busy condition is connected up so as to inform the calling subscriber (or operator in case the call is made by way of a manual board) that the number dialled is unobtainanble. As will be seen from the drawings, Fig. l, the busy signal is supplied by way of the cam assembly shown which is arranged to provide alternatively earthed high pitched tone and flash battery at suitable time periods. During the flash period, battery is connected by way of both windings of relay A to the calling circuit so as to release a supervisory relay in the controlling operators cord circuit to produce a busy flash signal at the manual board. Under these conditions relay A in the final selector circuit, is of course, released, and since the release period is considerably in excess of that which is covered by the normal slow releasing period of relay B a special cam assembly is provided, ar ranged to operate in synchronism with that previously mentioned so as to maintain a holding circuit to the left-hand winding of relay B during the flash condition. Upon the release of the connection at the end of the conversation, or alternatively during the busy or dead number connection, relays A and B will release in turn, the latter disconnecting the guarding and holding earth from the release trunk conductor to allow all preceding switches to restore, and moreover at its armature b7 completes a circuit to the release magnet ZM which energizes to remove the looking detent from the switch shaft, which then restores to the normal position. It will be noted that the release magnet ZlVl is equipped with two sets of springs designated zml and 21112, the former maintaining a guarding earth to the release trunk conductor to busy the switch until the wipers are actually in their home position, while at springs zm2 the energizing circuit is opened to relay WS.

Considering now the release condition on a no reply call, relays WS and AC will restore when the calling loop is opened and will be followed by relays BC, H, J and RN in turn. As relay RN is the last relay in the control equipment to restore to normal it is provided with an armature m5 arranged to bridge armature bc2 so as to maintain a guarding circuit to the control equipment until all the relays are in the normal position, the release of relay RN will free relay K and also the preceding switches.

I claim:

1. In a telephone system, a group of switches, groups of contacts accessible to said switches, a set of common controlling equipment, means for associating said equipment with any one of said switches, means in said equipment for operating the associated switch to connect with a group of contacts, and means for disassociating said equipment from said switch responsive to the switch connecting with a group of contacts which are either busy or unequipped.

2. A telephone system as claimed in claim 1 in which a distinctive signal is transmitted to the calling party after the disconnection of the control equipment.

'3. In a telephone system, a group of switches, lines accessible to said switches, a set of common control equipment and means for associating it temporarily with any one of said switches, means including said equipment for operating the switch to connect with a line, means responsive to the switch finding said line busy for further operating the switch to a predetermined position, and means controlled by the switch in said position for transmitting a busy signal to the calling party independent of said control equipment.

4. A telephone system as claimed in claim 3 in Which the switch is moved to the predetermined position under control of the common control equipment and in which the equipment is disconnected from the switch upon the switch responsive to the switch reaching such position.

5. In a telephone system, a group of final selectors, equipped and unequipped lines accessible to said selectors, controlling apparatus adapted to be associated temporarily with any one of said switches, means including said apparatus for op erating a switch to connect with one of said lines, and means for returning a distinctive signal to the calling party independent of said control apparatus in case the line is unequipped.

6. A telephone system as claimed in claim 3 in which the busy signal is transmitted via contacts mechanically closed by the switch when operated to the predetermined position.

7. In a telephone system, a group of switches, lines accessible to said switches, a set of common controlling equipment associated with said switches, means for connecting said equipment with any one of said switches individually, means including the equipment for operating the switch to connect with a called line, and a relay in said equipment adapted to respond to current flow in one direction only for testing the line connected with to determine its busy or idle condition.

8. A telephone system as claimed in claim 7 in which the test relay is an ordinary direct current relay with a metal rectifier included in its circuit.

9. A telephone system as claimed in claim '7 in which the test relay is a polarized relay.

10. In combination with a group of switches, controlling apparatus common to said switches, circuit connections for temporarily connecting said apparatus withany one of said switches individually, a test relay in said apparatus for controlling the switch, and a metal rectifier in said apparatus included in the circuit of said relay and controlling its testing operation.

11. In a telephone system, a group of switches, lines accessible to said switches, common controlling apparatus associated with said switches, means including said apparatus for operating a switch to extend a connection to a line, and means in said apparatus for applying a continuous signalling current to the line immediately upon the switch connecting therewith.

12. A telephone system as claimed in claim 11 in which a slow-acting relay in the controlling apparatus is adapted to disconnect the signalling current from the line after a predetermined inassociating it with any one of said switches, means including said equipment for operating the switch to extend a call to a line, a relay in said apparatus adapted to be operated responsive to the called line testing busy and responsive to the answering of a call in case the line tests idle, and means controlled by said relay for disconnecting said control equipment from the switch.

REGINALD TAYLOR. 

